High frequency excitation arrangements are necessary, for example, for excitation of a plasma for use in a gas laser (e.g., a CO2 laser). Other applications include deposition of thin layers and plasma etching. For plasma excitation, it is generally possible to input the power directly with a DC voltage or a low-frequency AC voltage. Alternatively, the coupling can take place capacitively through a dielectric with a high-frequency voltage.
German patent serial no. DE 43 22 608 C2 discloses a device that includes electrodes for capacitively coupling power into the plasma. The electrodes are connected to a voltage source through at least one resonant circuit and at least one output stage. The output stage includes two switching elements that can be inversely driven, and the switching signals of the switching elements can be supplied to the resonant circuit. The resonant circuit is a series resonant circuit and the modulation of the power coupling occurs starting from the resonant frequency by a variation of the switching frequency. A sine form voltage is generated by the series resonant circuit, which is present at the electrodes. The switching elements are driven by a driver circuit that requires a complex potential isolation of an auxiliary supply. If MOSFETs are used as the switching elements, high power loss occurs, because the gate source capacitance of the switching elements must be reloaded through the internal resistance of the driver circuit.